System and method for laser marking substrates

Abstract

A laser marking system comprises at least one controller to control an array of optical devices, between a laser source and a scan head. The array applies a selected pattern of portions of the received spatial profile of the laser beam to the substrate to achieve a second intensity different from the first intensity of laser beam at a rate of power deposition relative to a rate of thermal diffusion in the substrate for a predetermined time interval to thermally heat locations of the substrate with the selected pattern of the portions. The second intensity effectuates carbonization of materials of the substrate to create a mark without ablation.

1 . A method of laser marking a substrate comprising:
 positioning a substrate relative to a scan head of a laser marking system having a laser source that generates a laser beam of predetermined power and predetermined duration;   producing a laser beam having a first intensity; and   controlling, by at least one controller, a modulator, between the laser source and the scan head, to apply the laser beam to the substrate for a selected time interval to achieve a second intensity different from the first intensity of the laser beam at a rate of power deposition relative to a rate of thermal diffusion in the substrate for the selected time interval to thermally heat locations of the substrate with the laser beam wherein the second intensity effectuates carbonization of materials of the substrate without ablation to create a mark.   
     
     
         2 . The method of  claim 1 , wherein the controlling step comprises selecting a rise time and a fall time of the laser beam applied to the substrate, wherein the selected time interval is based on the rise time and the fall time. 
     
     
         3 . The method of  claim 1 , wherein the modulator is one of an electro-optic (EO) modulator, an acousto-optic (AO) modulator, a spatial-light-modulator (SLM), a metamaterial modulator (MM), and a liquid crystal (LC) modulator. 
     
     
         4 . The method of  claim 3 , wherein the controlling step comprises changing one or more material properties of the modulator to control a rise time and a fall time of the laser beam applied to the substrate, wherein the selected time interval is based on the rise time and the fall time. 
     
     
         5 . The method of  claim 1 , wherein the modulator comprises an array of optical devices, wherein the controlling step comprises transmitting, at a first time, a first signal to the array of optical devices such that the laser beam is applied to the substrate at the first time and transmitting, at a second time, a second signal to the array of optical devices such that the laser beam is not applied to the substrate at the second time, wherein the selected time interval is based on the first time and the second time. 
     
     
         6 . The method of  claim 5 , wherein the array of optical devices are an array of reflective optical elements, wherein the array of reflective optical elements are configured to reflect the laser beam at the substrate at the first time and wherein the array of reflective optical elements are configured to reflect the laser beam at a laser beam absorbing device at the second time. 
     
     
         7 . The method of  claim 5 , wherein the array of optical devices are an array of transmissive optical elements, wherein the array of transmissive optical elements are configured to transmit the laser beam at the substrate at the first time and wherein the array of transmissive optical elements are configured to transmit the laser beam at a laser beam absorbing device at the second time. 
     
     
         8 . The method of  claim 5  further comprising:
 directing the laser beam to the modulator having the array of optical devices; 
 pixelating the laser beam with the array of optical devices to create discrete laser beamlets; 
 depositing power on the substrate, between the first time and the second time, at the rate of the power deposition with selected beamlets of the discrete laser beamlets of the pixelated spatial intensity profile. 
 
     
     
         9 . The method of  claim 8  wherein the deposition of the power with the selected beamlets of the pixelated spatial intensity profile, includes:
 selecting a sequence of beamlets of the discrete laser beamlets, separated in time, between the first time and the second time; and 
 depositing power on the substrate, using the sequence of beamlets of the discrete laser beamlets, separated in time between the first time and the second time to provide for thermal separation to compensate for thermal diffusion at fixed locations of the power application to the substrate. 
 
     
     
         10 . The method of  claim 8  further comprising:
 scanning, by the scan head, in a scan pattern the selected beamlets of the discrete laser beamlets in a marking field of the substrate between the first time and the second time, wherein mirrors of the scan head are controlled to expose the substrate within the marking field to generate the mark within the marking field through carbonization of the materials. 
 
     
     
         11 . The method of  claim 2  wherein the array of optical devices comprises one of reflective devices and refractive devices; and
 further comprising: 
 directing, at the second time, by the array of optical devices, the laser beam to a beam absorber; and 
 absorbing, by the absorber, the laser beam directed thereto at the second time. 
 
     
     
         12 . The method of  claim 1  wherein the selected time interval to apply the controlled power deposition is based on carbonizing components of the material of the substrate, a rate of movement of the substrate, the first intensity of the laser beam, thermal conductivity of the substrate, and content of the mark wherein the thermal diffusion in the substrate being based on thermal conductivity of the substrate. 
     
     
         13 . The method of  claim 1  wherein the rate of the power deposition is based on a fall time and a rise time wherein the selected time interval is based on the fall time and the rise time. 
     
     
         14 . The method of  claim 1  further comprising:
 sensing, by a sensor, a condition of the mark generated on the substrate; 
 controlling, by the at least one controller in signal communication with the sensor and the laser source, the selected time interval of the power deposition applied to the substrate by the laser beam in response to the detected condition of the mark to effectuate further carbonization of materials of the substrate; and 
 repeating the sensing until a final carbonization level achieved. 
 
     
     
         15 . A laser marking system having a scan head for marking a substrate via carbonization of components of the substrate, the system comprising:
 a laser source that generates a laser beam of predetermined power, first spatial profile and predetermined duration;   a modulator between the laser source and the scan head; and   at least one controller to control the modulator, between the laser source and the scan head, to apply the laser beam to the substrate for a selected time interval to achieve a second intensity different from the first intensity of the laser beam at a rate of power deposition relative to a rate of thermal diffusion in the substrate for the selected time interval to thermally heat locations of the substrate with the laser beam wherein the second intensity effectuates carbonization of materials of the substrate to create a mark.   
     
     
         16 . The system of  claim 15 , wherein the modulator is one of an electro-optic (EO) modulator, an acousto-optic (AO) modulator, a spatial-light-modulator (SLM), a metamaterial modulator (MM), and a liquid crystal (LC) modulator 
     
     
         17 . The system of  claim 16 , wherein the controller is configured to transmit a signal to the modulator to change one or more material properties of the modulator to control a rise time and a fall time of the laser beam applied to the substrate, wherein the selected time interval is based on the rise time and the fall time. 
     
     
         18 . The system of  claim 15 , wherein the modulator comprises an array of optical devices, wherein the controller is configured to transmit, at a first time, a first signal to the array of optical devices such that the laser beam is applied to the substrate at the first time and wherein the controller is further configured to transmit, at a second time, a second signal to the array of optical devices such that the laser beam is not applied to the substrate at the second time, wherein the selected time interval is based on the first time and the second time. 
     
     
         19 . The system of  claim 18 , wherein the array of optical devices are an array of reflective optical elements, wherein the array of reflective optical elements are configured to reflect the laser beam at the substrate at the first time and wherein the array of reflective optical elements are configured to reflect the laser beam at a laser beam absorbing device at the second time. 
     
     
         20 . The system of  claim 18 , wherein the array of optical devices are an array of transmissive optical elements, wherein the array of transmissive optical elements are configured to transmit the laser beam at the substrate at the first time and wherein the array of transmissive optical elements are configured to transmit the laser beam at a laser beam absorbing device at the second time.